This invention relates to a system and method for adaptive streaming of data.
Online delivery of audio-video content is known, based around IP unicast streaming and downloading to web-based clients, mobile handsets, set-top boxes and connected television sets. Recent developments in this area have seen first-generation proprietary streaming protocols replaced with a raft of (still proprietary) approaches to unicast streaming from different vendors converging on the HTTP application protocol. These include Microsoft Smooth Streaming, Apple's HTTP Live Streaming and Adobe's HTTP Dynamic Streaming. Another point of convergence is that these second-generation delivery technologies introduce the concept of Dynamic Adaptive Streaming whereby the same source media is encoded at a number of different bit rates and qualities. The client then switches dynamically between these different media streams as the media presentation progresses according to available network bit rate and playback conditions, thereby minimising adverse visible or audible effects.
Multicast streaming has been suggested as a means of reducing bandwidth across both ISPs and cache and origin access. Because of its logical similarity to broadcasting (one way transmission from source to viewer), it is less suitable for on-demand streaming, non-real-time downloading or the recently introduced concept of “live rewind”. However, for live linear streams (e.g. a news channel) and for big events with high viewing figures (and therefore high unicast delivery costs) multicast offers an attractive technical solution for scaling provision to match audience demand.